GridLab, Eger, 31 Mar-1 Apr [email protected] Potential Gravitational Applications of Grid B.S. Sathyaprakash GridLab conference, 31

GridLab, Eger, 31 Mar-1 Apr 2003 [email protected]

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PotentialPotentialGravitational Applications of GridGravitational Applications of Grid

B.S. SathyaprakashGridLab conference, 31 Mar-1 April, Eger, Hungary


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Modern AstronomyModern Astronomy

Cosmic micro-wave background and big bang

Optical, radio, x- and gamma-ray telescopes have revealed a lot of new objects and Optical, radio, x- and gamma-ray telescopes have revealed a lot of new objects and phenomenaphenomena

PulsarsPulsarsX-ray binaries; gamma-ray X-ray binaries; gamma-ray

emitting sourcesemitting sources

Supermassive Black Supermassive Black holesholes

Quasars and Radio Quasars and Radio galaxiesgalaxies


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Astronomy has taught us that more than 90% of the Universe is dark

Even this dark matter interacts gravitationally; we should be able to ‘see’ this matter via

gravitational radiation it might emit

But ...


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Plan of the talkPlan of the talk Gravitational waves

brief overview of gravitational wavesbrief overview of gravitational waves astronomical sourcesastronomical sources interferometric detector projects around the interferometric detector projects around the

worldworld Gravitational wave data analysis and Grid

large data setslarge data sets big collaborations big collaborations huge data base recordshuge data base records


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Gravitational Waves - A simple and Gravitational Waves - A simple and brief overview of the theorybrief overview of the theory


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Newton’s law of GravityNewton’s law of Gravity The force of gravity between

two masses m and M separated by a distance r is

F = G m M / r2

Newton’s law of gravity transmits force instantaneously - if body M changes its position it is felt by instantaneously by body m

If Newton’s gravity is right we will be able to build a ‘gravitational telegraph’ which can transmit signals instantaneously - a violation of Einstein’s special relativity


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Ripples in the Fabric of Ripples in the Fabric of SpacetimeSpacetime

Gravitational disturbances too travel at a finite speed - indeed the same speed as light. This is what we call gravitational waves

According to Einstein gravity is nothing but warping of spacetime

Therefore, gravitational waves are ripples in space-time warping that propagates at the speed of light.


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Do Gravitational Waves Exist? Do Gravitational Waves Exist? Inspiral in Hulse-Taylor binary pulsarInspiral in Hulse-Taylor binary pulsar

Two neutron stars in orbit Each has mass 1.4 times the Each has mass 1.4 times the

mass of the Sun; Orbital period mass of the Sun; Orbital period 7.5 Hrs7.5 Hrs

stars are whirling around each stars are whirling around each other at a thousandth the other at a thousandth the speed of lightspeed of light

Eventually the binary will coalesce emitting Eventually the binary will coalesce emitting

a burst of GW that will be observable usinga burst of GW that will be observable using

instruments that are currently being builtinstruments that are currently being built

But that will take But that will take another 100 million another 100 million

yearsyears

According to Einstein’s theory According to Einstein’s theory the binary should emit GW the binary should emit GW

GW carry rotational energy from GW carry rotational energy from the system which causes the two the system which causes the two stars to spiral towards each other stars to spiral towards each other and a decrease in the periodand a decrease in the period

Observed period change is about Observed period change is about 10 micro seconds per year10 micro seconds per year

This decrease in period is This decrease in period is exactlyexactly as predicted by Einstein’s theoryas predicted by Einstein’s theory


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Stellar mass GW sources - observable Stellar mass GW sources - observable from groundfrom ground

Supernovae and birth of black holes

Spinning neutron stars in X-ray binaries

Relativistic Instabilities in young NSBinaries of black holes & neutron stars


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GW Sources observable from spaceGW Sources observable from space

Merging super-massive black holes in galactic centers

Signals from gravitational capture of small black holes by super-massive black holes


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Observing the origin of the UniverseObserving the origin of the Universe


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Gravitational Wave DetectorsGravitational Wave Detectors


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Interaction of Gravitational Waves Interaction of Gravitational Waves

Plus polarizationPlus polarization Cross polarizationCross polarization


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Laser Interferometric Detectors Laser Interferometric Detectors Basic Principle of OperationBasic Principle of Operation

LaserBeam Splitter

Photo Diode

Mirror

Mirror

Laser Beam


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LIGO

VIRGO

GEO

TAMA

ACIGA

LISA


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Searching for Gravitational WavesSearching for Gravitational WavesHow Grid Technology Can HelpHow Grid Technology Can Help


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A list of the problemsA list of the problems Computationally limited searches - bigger

computers means better science Hundreds of collaborators requiring to

access data from a network of detectors distributed round the world

Events are rare but data is poor with large false alarm rates - need to examine subsidiary channels of information

A large number of database records - making sense out of garbage


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What are we up against?What are we up against?Large Data Rates Large Data Rates

environmental background seismic disturbancesseismic disturbances solar flares and magnetic solar flares and magnetic

storms, cosmic rays, ...storms, cosmic rays, ... instrumental noise

electronic noise in electronic noise in feedback systems, laser feedback systems, laser frequency and intensity frequency and intensity noise, thermal noise, thermal fluctuations in mirrors, fluctuations in mirrors, vibration of suspension vibration of suspension systems, ...systems, ...

Important to understand detectors before any analysis begins a large number of channels a large number of channels

are collected to record are collected to record detector state - any analysis detector state - any analysis should look at all this datashould look at all this data

Interferometers collect data at rates of order 10 Mbytes per second, 24/7; 300 Tbytes per year We want to be able analyse We want to be able analyse

at least part of that dataat least part of that data


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Distributed dataDistributed data Interferometer projects work collaboratively -

all data is accessible everyone in the collaboration wherever in the world they may be

How do we make all this data available to the community? data replication to multiple sites - GriPhyN, Trianadata replication to multiple sites - GriPhyN, Triana guaranteeing data integrity guaranteeing data integrity data discovery tools and P2P data accessdata discovery tools and P2P data access


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Types of gravitational wave signalsTypes of gravitational wave signals Transients - last for a

short duration so that detector motion can be neglected Transients with known Transients with known

shape, e.g. black hole shape, e.g. black hole binariesbinaries

Transients with unknown Transients with unknown shape, e.g. supernovaeshape, e.g. supernovae

Stochastic backgrounds population of population of

astronomical sourcesastronomical sources primordial stochastic primordial stochastic

gravitational wave signalsgravitational wave signals

Continuous waves - last for a duration long enough so that detector motion cannot be neglected Typically very weak Typically very weak

amplitude, signal power a amplitude, signal power a billion times smaller than billion times smaller than noise power noise power

long integration times long integration times neededneeded

slowly changing slowly changing frequency depending on frequency depending on several parametersseveral parameters


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Near all-sky sensitivityNear all-sky sensitivity

All sky sensitivity Quadrupolar antenna Quadrupolar antenna

patternpattern multiple detectors to multiple detectors to

determine direction determine direction to sourceto source

Wide band sensitivity 1 kHz around 100 Hz1 kHz around 100 Hz


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Why GW data analysis challenging?Why GW data analysis challenging? Signals with known shapes but unknown parameters

large parameter spacelarge parameter space for example, 10 parameters in black hole binary searchfor example, 10 parameters in black hole binary search

great number of wave cycles to integrategreat number of wave cycles to integrate for example, 10for example, 1010 10 wave cycles in a year from a neutron starwave cycles in a year from a neutron star

Signals of unknown shape uncertain and inaccurate, physical modelsuncertain and inaccurate, physical models

for example waves from supernovae and black hole collisionsfor example waves from supernovae and black hole collisions

Very weak signal strengths long integration timeslong integration times

for example up to a year for neutron star signalsfor example up to a year for neutron star signals a lot of pixels on the sky due to Doppler modulationa lot of pixels on the sky due to Doppler modulation

Implies the need for large computational resources


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Compute-intensive searches - An Compute-intensive searches - An exampleexample

Searching for black hole binaries that last for about a few seconds in the detector band A pattern matching A pattern matching

technique is employed since technique is employed since the signal shape is known, the signal shape is known, but ...but ...

signal parameters are not signal parameters are not known before handknown before hand

must filter the data through must filter the data through a large number of templates a large number of templates corresponding to different corresponding to different parametersparameters

a search in a 10-dimensional a search in a 10-dimensional spacespace

Triana is currently implementing this search on a compute cluster to be extended using Grids

issues - distributed data, on-line search, load balancing

data serial search is preferred due to astrophysical reasons


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Knowledge discoveryKnowledge discovery Not all problems are computational resource

intensive - some can be handled computationally, for example short bursts of unknown shape as in supernovae, but produce huge data bases millions of records inserted into the database each daymillions of records inserted into the database each day must go back to the original data set to veto out false must go back to the original data set to veto out false

alarms (that is, spurious non-GW events produced by alarms (that is, spurious non-GW events produced by instrumental and environmental background)instrumental and environmental background)

need an automatic bridge between analysis pipeline and need an automatic bridge between analysis pipeline and databasedatabase

Database query functionality built into Triana ...


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Two searches that urgently require Two searches that urgently require grid technologygrid technology

Searching for black hole binaries large parameter spacelarge parameter space

masses, spins, masses, spins, orientations, orientations,

need to go back to need to go back to numerical simulations numerical simulations that produced the that produced the templates and to refine templates and to refine the searchthe search

need to analyse need to analyse thousands of subsidiary thousands of subsidiary channels to confirm or channels to confirm or veto out eventsveto out events

All sky search for neutron stars week signals warranting week signals warranting

integration of large data integration of large data setssets

Doppler modulation in Doppler modulation in the signal caused by the the signal caused by the motion of the detector motion of the detector means billions of pixels in means billions of pixels in the skythe sky

currently the search is currently the search is restricted to targeted restricted to targeted known sourcesknown sources


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Scientific rewards from GW Scientific rewards from GW observationsobservations

(Very) Early Universe

Gravitational WaveObservations

Solar, stellar interiorsCosmology

Quantum theory

Astrophysics

Fundamental physics Extreme Gravity

Documents

GridLab, Eger, 31 Mar-1 Apr [email protected] Potential Gravitational Applications of Grid B.S. Sathyaprakash GridLab conference, 31